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Sunday, January 30, 2011

I was over at Rocky Mountain Computer Repair last night looking over some of the dead machines that had been abandoned by their customers. Most machines were old and rather junky looking, but a few are in decent condition, except for the fact that they simply do not turn on at all.

One laptop in particular wouldn't post, and I figured it was either due for a motherboard replacement, or just maybe I would see something visibly wrong that I could repair. So an hour of disassembly, some fairly rigorous testing of potential faults, and I concluded that the motherboard was dead.

This would usually be the moment to either abandon the machine or buy a replacement motherboard. However, I have an engineering degree that has put me in a lot of deep contact with computers and I have learned some extra tricks as to what it takes to fix them that aren't exactly in the manual.

So here is the situation:

An apparently completely intact laptop computer will not post

No visible impact damage

No visible fire or heat damage

Functional and tested power supply

System starts to initialize but shuts down after 1 or 2 seconds, and before post

No audible alarms

The laptop motherboard clearly had some function components, as it would attempt to start, however some pretty critical component needed early in the initialization process was not functioning, thus causing the machine to shut down.

Given the symptoms, the most likely culprit was the nvidia northbridge or maybe the CPU. However since there were no alarms indicating a cpu or memory failure, the issue likely lay with the northbridge which is intricately involved with initializing both those systems.

And how do you repair a northbridge?

Well, you don't. If the chip is genuinely dead then there is nothing to be done and it is officially time for a new motherboard. However, if the chip is still good (and there isn't a really good way to diagnose this short of desoldering and testing in a laboratory setting), then the problem likely lies with the connections between the chip and the board. And perhaps those connections can be re-established by heating the board to a point near to the melting point of solder.

So here is what we did:

Removed all plastic and tape from the board

Wrapped board in tin-foil and placed foil padding against steel grate

Pre-Heated toaster oven to 385F

Placed board in oven

Chilled out for 6 minutes

Removed board from oven

Let it cool for 10 minutes

Installed CPU and Memory

Reconnected board to laptop power supply, power button and screen

Pushed the power button

The board posted, and a moment later was complaining that it was missing an operating system and would we please give it back its hard drive. This process is known as reflowing, and although it won't fix all similar issues it may just provide a solution to those in need.